Human flavor and food preferences established early in life track into childhood and adolescence, a finding with important implications for long-term health. How such preferences develop remains a mystery, however. The primary goal of our research program is to understand how flavor and food preferences develop and are modified with experience. To this end, we investigated the very earliest flavor experiences, those which occur in utero and during breastfeeding, and demonstrated that these experiences influence the infant's acceptance of a variety of flavors and foods including vegetables. More recently, we have taken advantage of the marked flavor differences among commercial infant formulas as a model to study the effects of early experiences in infants who are formula fed. The drastic developmental changes in acceptance of formulas which are protein hydrolysate based and the finding that early exposure results in a complete shift in hedonic tone to the flavor of this formula from one of absolute distaste to eager acceptance, make it a powerful experimental tool. The effects of early exposure were particularly persistent, leading to altered preferences several years after the child's last exposure. The findings from these studies set the stage for the proposed investigation on sensitive periods in determining flavor and food preferences ("flavor imprinting"). To maximize the value of this research, most of the proposed studies are conducted with the same cohort of infants. These infants will be studied across their first three years of life, a period we believe is crucial to the establishment of long-term patterns of flavor and food acceptance. The results of this novel, multidisciplinary research program will have both theoretical and practical implications for understanding the sensory-guided responses of human infants and the biology of food choice. They will also provide information on strategies to overcome the difficulties in introducing hydrolysate formulas to infants who need them clinically. Children participating in each of the proposed studies will be genotyped for recently discovered taste receptor genes to determine how genetic differences contribute to the development of food preferences. New knowledge about the mechanisms underlying the formation of food preferences and the molecular basis of food likes and dislikes in children, a generation who will struggle with obesity and diabetes, may suggest strategies to overcome diet-induced diseases. [unreadable] [unreadable]